A battery apparatus can include one or more battery packs being coupled in parallel, and each of the battery packs may include a plurality of batteries. Thus, different voltage and/or power requirements of portable computers, medical treatments, test instruments and other industry applications, may be satisfied by different arrangements of the battery apparatus. However, since the capacity of a battery apparatus may be limited to the capacity of a battery that has the lowest capacity among the series-coupled batteries when its capacity does not match the others, the overall capacity of such a battery apparatus may be reduced, which can affect its application.